1. Field of the Invention
The invention relates to pneumatic controls for dispensing materials at the end of a robot arm. More specifically, the invention relates to an integral pneumatic control system and a method for controlling same to eliminate fluctuations in material flow rates.
2. Description of the Related Art
The manufacture of goods can often require the application of viscous materials. These materials may be used to paint, seal, coat, adhere, weld and the like. The material must be applied in a uniform and automated fashion. In many instances, the material is directed by a robot that has been programmed to apply materials to the items being manufactured or treated.
Dispensing materials out of a gun at the end of a robot arm is difficult, especially as the viscosity of the material being applied grows. Dispensers that perform such tasks are large and incapable of being located at the end of a robot arm. Problems arise when the dispensers increase the cycle time of production merely because the reloading time required approaches the magnitude of minutes. Another issue relating to automatically dispensing material relates to inventory control. If control of the volume of material is not good, it will be difficult to determine when the system will need to be reloaded. Further, it will also be difficult to determine just how much material is required to complete a task for a particular piece or part.
One attempt to overcome the deficiencies in reloading dispensers is disclosed in U.S. Pat. No. 4,701,112, issued to Eisenhut et al. on Oct. 20, 1987. This reference discloses a pumping system having two fluid pumps. Two reed switches indicate a fully loaded reservoir and an empty reservoir. The reed switch configuration is found on each of the fluid pumps. As the fluid in one reservoir is emptied, a reed switch indicates this condition. It turns off the pump associated with that reservoir and turns the pump on for the other reservoir. This system is deficient because the switching between reservoirs occurs in an abrupt fashion. There is no moderate transition between the two reservoirs. If this pumping system were employed in an automated assembly line, some parts may pass the robot without receiving an adequate amount of the material or the application of the material will be uneven. In many application scenarios, this abrupt switch-over from one reservoir to another will not be acceptable.
A robot assembly is disclosed for applying a material to a part. The robot assembly includes a robot arm that is movable through a plurality of axes pursuant to a given set of instructions. The robot arm includes a plurality of elements, each separated by at least one joint. The robot arm extends between a base end and a distal end. A pneumatic dispensing system is used in conjunction with the robot arm for dispensing the material from the distal end of the robot arm onto the part. The pneumatic dispensing system controls the volume and speed at which the material is applied to the part. The robot arm determines where the material is applied with respect to the part. A robot controller controls the position, orientation, and speed of movement of the robot arm with respect to the part as the robot arm moves through its designated motion. The robot controller also controls the volume of the material being applied to the part by the pneumatic dispensing system.